Fatma I. Khattab

Thermal analysis of pharmaceutical compounds. V. The use of differential scanning calorimetry in the analysis of certain pharmaceuticals

Abstract Differential scanning calorimetric (DSC) analysis was carried out for some interesting pharmaceutical compounds which have different thermal characteristics. The compounds investigated were phenacetin, cholesterol myristate, sulphathiazole, sulphadiazine, sulphadimethyloxazole, sulphamerazine and sulphadimidine. The DSC scans of the compounds were thoroughly studied and the pronounced features for each are given, including their behaviour on fusion. It is confirmed that some of the examined pharmaceuticals, such as sulphathiazole. sulphadiazine and sulphadimethyloxazole, exist in polymorphic forms. The information obtained is useful in interpreting the results of the examination of the compounds by thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA) and their melting point determinations using the Kofler microscope. The heat of reaction is calculated for all the reactions of the compounds studied. The possibility of purity determination of the examined compounds by a thermoanalytical method was studied. The DSC method was found to be suitable for the purity determination of sulphamerazine and sulphadimidine in addition to phenacetin for which the method is known to be applicable. The remaining compounds, on the other hand, do not exhibit the required characteristics for the determination of purity by the DSC method. DSC was also found to contribute to stability studies, where sulphathiazole was found to be the least stable among the examined sulphonamides.

Thermal analysis of urea, fatty acids, and their adducts

Abstract The thermal analysis of urea and its decomposition product, biuret, was achieved. The calorimetric method was found to be suitable for the determination of the purity of urea. Some selected fatty acids varying in chain length and saturation (butyric, caproic, lauric, myristic, palmitic, stearic and oleic acid) were also examined. Attempts at their characterization and identification were successful. Determination of their boiling or melting points was possible by thermal analysis. The possibility of adduct formation between urea and fatty acid was also studied using either the dissolved urea technique or simply by physical mixing. The stability of the formed adducts, mechanism of dissociation, their dissociation temperatures and heat of reaction (Δ H ) were also investigated. The boiling point, melting point, Δ H values and decomposition temperatures for each series studied were found to increase with chain length and decrease with unsaturation. Various thermal analysis techniques were used, namely, diferential thermal analysis (DTA), differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG).

Multi-residues determination of antimicrobials in fish tissues by HPLC–ESI-MS/MS method

A rapid, simple, sensitive and specific LC-MS/MS method was developed and validated for the simultaneous quantification of four antimicrobials commonly used in aquaculture, namely ciprofloxacin (CPX), trimethoprim (TMP), sulphadimethoxine (SDM) and florphenicol (FLOR) in fish tissues. The LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. Sample preparation involves simple liquid extraction step followed by post-extraction clean-up step with n-hexane. The purified extracts were chromatographed on Agilent Poroshell 120 EC, C18 (50 mm × 3 mm, 2.7 μm) column by pumping an isocratic mobile phase consisting of 0.1% formic acid in water:0.1% formic acid in methanol (20:80, by volume) at a flow rate of 0.4 mL/min. A detailed validation of the method was performed as per FDA guidelines and the standard curves were found to be linear in the range of 1-100 ng/g for both CPX and TMP, 0.5-100 ng/g for SDM and 1-50 ng/g for FLOR. The intra-day and inter-day precision and accuracy of the results were within the acceptable limits. A run time of 1.5 min for each sample made it possible to analyze multiple fish tissue samples per day. The developed assay method was successfully applied for the detection of antimicrobials in real fish tissue samples obtained from different fish farms.

Stability-Indicating Methods for the Determination of Ornidazole in The Presence of its Degradate According to ICH Guidelines

Four simple, sensitive, selective and precise methods were developed for the determination of Ornidazole (OZ) in presence of its degradation product. The first method was based on first derivative spectrophotometry D1 and measuring the peak amplitude of D1 spectra at 290.4 and 332 nm. The second method was depended on measuring the peak amplitude of the first derivative of the ratio spectra DD1 at 288.5 and 328 nm. The third method was the mean centering of the ratio spectra one (MCR), which allowed the determination of OZ in presence of its degradate and the concentration of OZ was determined by measuring the amplitude at 312.8 nm. Separation and determination of OZ by HPLC in the forth method was achieved using Lichrosorb RP-18 column and acetonitrile: water, (50:50v/v), 0.2% triethylamine, the pH was adjusted to 4 using o-phosphoric acid. The flow rate was 1 mL min-1. Beer’s law was obeyed in concentration range 5–30 μg/ml for the first three methods. The linearity range in the forth method was 2-20 μg/ml. The proposed methods were used to determine OZ in its pure powdered form with mean percentage recoveries of 99.86 ± 1.249% and 99.98 ± 0.868% for OZ at 290.4 and 332 nm respectively, in D1 method. In DD1 method, the mean percentage recoveries were 100.11 ± 1.020% and 100.15 ± 1.043% at 288.5 and 328 nm respectively. While in MCR and HPLC methods, the mean percentage recoveries were 100.09 ± 0.387% and 100.00 ± 1.302% respectively. The degradation product was obtained in alkaline stress condition, separated, and identified by LC-MS spectral analysis, from which the degradation product was confirmed. The four methods were validated according to International Conference on Harmonization. The four methods were found to be specific for OZ in presence of up to 80% of its degradation product in the first three methods. The four proposed methods were successfully applied for the determination of OZ in Tibezole® tablets. Statistical comparison between the results obtained by these methods and the reported method for the determination of the drug in its pharmaceutical formulation was done, and it was found that there was no significant difference between them.

Validated spectrophotometric methods for simultaneous determination of troxerutin and carbazochrome in dosage form

Four simple, accurate, sensitive and precise spectrophotometric methods were developed and validated for simultaneous determination of Troxerutin (TXN) and Carbazochrome (CZM) in their bulk powders, laboratory prepared mixtures and pharmaceutical dosage forms. Method A is first derivative spectrophotometry (D(1)) where TXN and CZM were determined at 294 and 483.5 nm, respectively. Method B is first derivative of ratio spectra (DD(1)) where the peak amplitude at 248 for TXN and 439 nm for CZM were used for their determination. Method C is ratio subtraction (RS); in which TXN was determined at its λmax (352 nm) in the presence of CZM which was determined by D(1) at 483.5 nm. While, method D is mean centering of the ratio spectra (MCR) in which the mean centered values at 300 nm and 340.0 nm were used for the two drugs in a respective order. The two compounds were simultaneously determined in the concentration ranges of 5.00-50.00 μg mL(-1) and 0.5-10.0 μg mL(-1) for TXN and CZM, respectively. The methods were validated according to the ICH guidelines and the results were statistically compared to the manufacturers method.

Simultaneous determination of metronidazole and spiramycin in bulk powder and in tablets using different spectrophotometric techniques

Metronidazole (MZ) is an anti-infective drug used in the treatment of anaerobic bacterial and protozoa infections in humans. It is also used as a veterinary antiparasitic drug. Spiramycin (SP) is a medium-spectrum antibiotic with high effectiveness against Gram-positive bacteria. Three simple, sensitive, selective and precise spectrophotometric methods were developed and validated for the simultaneous determination of MZ and SP in their pure form and in pharmaceutical formulations. In methods A and B, MZ was determined by the application of direct spectrophotometry and by measuring its zero-order (D(0)) absorption spectra at its λ(max) = 311 nm. In method A, SP was determined by the application of first derivative spectrophotometry (D(1)) and by measuring the amplitude at 218.3 nm. In method B, the first derivative of the ratio spectra (DD(1)) was applied, and SP was determined by measuring the peak amplitude at 245.6 nm. Method C entailed mean centering of the ratio spectra (MCR), which allows the determination of both MZ and SP. The methods developed were used for the determination of MZ and SP over a concentration range of 5-25 µg ml(-1). The proposed methods were used to determine both drugs in their pure, powdered forms with mean percentage recoveries of 100.16 ± 0.73 for MZ in methods A and B, 101.10 ± 0.90 in method C, 100.09 ± 0.70, 100.02 ± 0.88 and 100.49 ± 1.26 for SP in methods A, B and C, respectively. The proposed methods were proved using laboratory-prepared mixtures of the two drugs and were successfully applied to the analysis of MZ and SP in tablet formulation without any interference from each other or from the excipients. The results obtained by applying the proposed methods were compared statistically with a reported HPLC method and no significant difference was observed between these methods regarding both accuracy and precision.

Spectrophotometric determination of some pharmaceutically active amides and imides

Abstract The determination of nicotinamide, alloxan, saccharin, barbitone and theobromine is achieved by a simple and rapid spectrophotometric method. The proposed method depends on the bromine oxi...

Validated univariate and multivariate spectrophotometric methods for the determination of pharmaceuticals mixture in complex wastewater.

Five, accurate, precise, and sensitive univariate and multivariate spectrophotometric methods were developed for the simultaneous determination of a ternary mixture containing Trimethoprim (TMP), Sulphamethoxazole (SMZ) and Oxytetracycline (OTC) in waste water samples collected from different cites either production wastewater or livestock wastewater after their solid phase extraction using OASIS HLB cartridges. In univariate methods OTC was determined at its λmax 355.7 nm (0D), while (TMP) and (SMZ) were determined by three different univariate methods. Method (A) is based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method followed by ratio difference method for determination of TMP and SMZ. Method (B) is successive derivative ratio technique (SDR). Method (C) is mean centering of the ratio spectra (MCR). The developed multivariate methods are principle component regression (PCR) and partial least squares (PLS). The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs. The obtained results are statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision at p=0.05.

Comparative Study of Different Chromatographic Techniques for the Analysis of Multi-Residues of Some Approved Antimicrobials in Fish Tissues

Two chromatographic methods were developed, optimized and validated for the simultaneous determination of three approved aquaculture antimicrobials, namely sulphadimethoxine sodium, trimethoprim and florphenicol in fish tissues. The developed methods were based on simple liquid extraction technique. The first method employs thin-layer chromatography as a clean-up procedure coupled with densitometric determination for the separated drugs. The second method is an HPLC one using X-Terra™ C18 column. Several mobile-phase systems and extracting solvents were tried to optimize the separation and the extraction procedures from fish tissues. The procedures were applied for the analysis of spiked fish tissue samples at three different concentration levels (10, 50 and 100 ppm). A comparative study was conducted between the proposed methods to discuss the advantage of each one. The methods were validated according to the international conference on harmonization guidelines. The proposed methods were successfully applied for the determination of the studied drugs in spiked fish tissues, pure powders and in their veterinary pharmaceutical formulation.

Determination of fluoroquinolone antibiotics in industrial wastewater by high-pressure liquid chromatography and thin-layer chromatography-densitometric methods

Two methods were described for the simultaneous determination of ciprofloxacin HCl (CIP) and moxifloxacin HCl (MOX) in their binary mixture present in industrial wastewater. A solid-phase extraction procedure (SPE) based on retention on HLB OASIS cartridges and elution with a mixture of methanol-water in acidic medium was preformed, and then both fluoroquinolones were separated using two chromatographic methods. The first method was based on high-performance liquid chromatographic separation of the two drugs on reversed-phase Zorbax C18 column. The mobile phase consisted of monobasic potassium phosphate (50 mM, pH 2.5, adjusted with phosphoric acid) and acetonitrile (80:20, v/v). Flow rate was 1 mL min−1. Quantitation was achieved with ultraviolet (UV) detection at 278 nm. Linearity was found to be over the concentration range of 1–50 µg mL−1 for both CIP and MOX. The second method was based on the thin-layer chromatographic (TLC) separation of the two drugs followed by densitometric measurements of their bands at 278 nm. The separation was carried out on silica gel 60 F254 plates, using methanol, ammonia, and methylene chloride (55:35:20, v/v) as a developing system. The linearity was found to be in the range of 0.25–2.5 µg band−1 for both CIP and MOX. Both methods were optimized and validated as per International Conference on Har-monization (ICH) guidelines. Separation was developed on spiked water samples and checked on process wastewaters of industrial origin after SPE sample pretreatment.